When a voltage is applied to an organic electroluminescence device (hereinafter referred to as an “organic EL device”), holes are injected from an anode into an emitting layer and electrons are injected from a cathode into the emitting layer. The injected holes and electrons are recombined in the emitting layer to form excitons. Here, according to the electron spin statistics theory, singlet excitons and triplet excitons are generated at a ratio of 25%:75%.
The organic EL device is applied to a display of a mobile phone and a television set. It is desired to further improve luminescence properties such as a luminous efficiency and an emission lifetime of the organic EL device.
For instance, Patent Literatures 1 to 8 each disclose an organic EL device in which a plurality of emitting layers are laminated in order to improve luminescence properties.